The present invention relates to a scroll compressor.
Generally, a scroll compressor includes a fixed scroll, which is fixed to a housing, and a movable scroll, which orbits with respect to the fixed scroll. The fixed scroll includes a fixed base plate and a fixed spiral wall projecting from the fixed base plate. The movable scroll includes a movable base plate and a movable spiral wall projecting from the movable base plate. The fixed spiral wall and the movable spiral wall are engaged with each other to define a compression chamber. The orbital movement of the movable scroll decreases the volume of the compression chamber and compresses refrigerant.
Japanese Laid-Open Patent Publication No. 2004-144045 describes an example of a scroll compressor that includes an elastic body arranged between the housing and the movable base plate of the movable scroll. A reactive force produced by a compression stroke produces a reactive force that acts on the movable scroll in the thrust direction. The elastic body counters the reactive force to enhance the sealing of the compression chamber.
Referring to FIG. 7, a scroll compressor 110 of the publication includes a housing 100, which accommodates a movable scroll 101 including a movable base plate 102. An elastic body 103 (sealing member) is arranged on the back surface of the movable base plate 102. The elastic body 103 is flat and annular and made of a metal material such as a carbon tool steel. In the housing 100, an opposing wall 105 is arranged at the side of the movable scroll 101 facing away from the fixed scroll 104. The opposing wall 105 faces toward the movable scroll 101. The back surface of the movable base plate 102 includes a contact portion 102a. The elastic body 103 is fixed in the housing 100 between the movable scroll 101 and the opposing wall 105 so that the elastic body 103 and the contact portion 102a are pressed against each other. The pressing between the elastic body 103 and the contact portion 102a is ensured at any orbital position of the movable scroll 101 relative to the fixed scroll 104.
In the housing 100, a back pressure chamber 107 (back pressure region) is defined at the inner side of the contact portion 102a. The pressing between the elastic body 103 and the contact portion 102a seals the back pressure chamber 107 from the region at the outer side of the contact portion 102a in the housing 100. The supply of refrigerant to the back pressure chamber 107 generates pressure (back pressure) acting to urge the movable scroll 101 toward the fixed scroll 104. This enhances the sealing of the compression chamber 108.
In addition, the opposing wall 105 includes a recess 105a that allows for elastic deformation of the elastic body 103. The pressing between the elastic body 103 and the contact portion 102a elastically deforms the elastic body 103 toward the opposing wall 105. The deformed elastic body 103 produces a resilient force that acts to restore the original shape of the elastic body 103. This urges the movable scroll 101 toward the fixed scroll 104. Thus, the movable scroll 101 is urged toward the fixed scroll 104 even when the back pressure in the back pressure chamber 107 is insufficient such as when the scroll compressor 110 starts to operate. This enhances the sealing of the compression chamber 108.
However, the elastic body 103 of the scroll compressor 110 is made of metal. Thus, the pressing between the elastic body 103 and the contact portion 102a may not be able to sufficiently seal the back pressure chamber 107 from the region at the outer side of the contact portion 102a in the housing 100. This may result in the leakage of refrigerant from the back pressure chamber 107 to the region at the outer side of the contact portion 102a in the housing 100.
During a normal operation of the scroll compressor 110, the movable scroll 101 is urged toward the fixed scroll 104 by the urging force produced by the elastic deformation of the elastic body 103, as well as the urging force produced by the back pressure in the back pressure chamber 107. When the urging force of the back pressure in the back pressure chamber 107 sufficiently urges the movable scroll 101 toward the fixed scroll 104 and enhances the sealing of the compression chamber 108, the urging force produced by the elastic deformation of the elastic body 103 would result in excessive pressing of the movable scroll 101 against the fixed scroll 104. This increases the sliding resistance between the movable scroll 101 and the fixed scroll 104 when the movable scroll 101 orbits. The sliding resistance causes mechanical loss during normal operation of the scroll compressor 110.